medwireNews: Hospital admission for infections in childhood is associated with an increased risk for being diagnosed with nonaffective psychosis later in life, research indicates.

The findings, published in Schizophrenia Bulletin, suggest that this association is largely driven by bacterial and central nervous system infections and that preadolescence is a particularly susceptible time.

Researchers Åsa Blomström (Karolinska Institutet, Stockholm, Sweden) and colleagues found that the risk for developing nonaffective psychosis, which occurred in 4638 (0.4%) of 1,172,879 children studied, was increased a significant 10% for those who were hospitalized with an infection between the ages of 0 and 13 years.

This was after taking into account potential confounders, such as gender, season, urbanicity, parental age and psychiatric history, maternal infections, and socioeconomic status.

The increased risk associated with infection was greatest for those who had a bacterial infection, at 23%, rather than a viral or other infection, and particularly if it was contracted between the ages of 10 and 13 years (preadolescence), at 57%.

Central nervous system infections were only significantly associated with the risk for developing nonaffective psychosis if contracted during preadolescence, increasing the likelihood by 96%.

The researchers also found that the risk for developing nonaffective psychosis increased with multiple admissions for any infection, from 10% for children admitted to hospital once to 37% for those admitted at least four times.

Blomström et al say their findings suggest that individuals who later develop nonaffective psychosis might have subtle immune deficiencies that render them more susceptible to early-life infections. But whether these infections have a causal role or reflect a vulnerability that may be associated with other social or genetic risk factors remains to be determined.

The current findings are corroborated in another study in the same journal, in which individuals hospitalized with an infection were found to be 41% more likely than others to be later diagnosed with schizophrenia.

The study involved 843,390 individuals, 3409 of whom were diagnosed with schizophrenia. And of these, 1549 (45%) had been admitted to hospital with an infection prior to diagnosis.

The researchers, led by Philip Nielsen (Aarhus University, Denmark), also found that bacterial infections were associated with the greatest increase in risk, at 63%, and that there was a dose–response relationship. But age at the time of infection did not appear to have a significant effect.

The team notes that hepatitis and genital infections were particularly associated with the risk for later schizophrenia, but that all sites of infection were associated with an increased risk.

This gives weight to there being a common underlying mechanism, “possibly one that involves an inflammatory response and the immune system,” they write.

“Future studies that can establish more explicit links between specific infectious agents and schizophrenia may provide pathways toward prevention,” the researchers conclude.